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WILLIAM J. BALDWIIT, 



^ 



An Outline of Ventilation 



—AND 



WARMING, 

Wm. J. Baldwin, m. am. soc. c. e., 



1 



Mem. Am. Soc. Mechs. Eiigs 

^l' KXPBRT 



— AND — 



CONSULTING ENGINEER 

— IN — 

Heating and Ventilation. 

( Copyrighted, iSgg.) 
Prick, One: DollAjr. 



^o 



Published by the Author,^^^- 
No. io6 and io8 Beekman Street, 
New York. 



THioiz. 



\HE Author is tlie pioneer writer in i 

.- America on tlie subject of Steam j 
Heating. 

His work "BALDWIN on HEATING," 
lias reaoliecL tlie Mtli edition. Price $2.60. 

Hi3 work "HOT WATER HEATING 
AND PITTING" is in t lie 3rd edition. 
Price, 12.60. 

Tliey are tlie standard American works 
of reference on these subjects. 



By Trs.a*^i^ 









-? 



LAST year the author published a little blue 
book, called ^^ Data for Heating and Ventil- 
ation/' and in its preface he promised to continue 
his efforts in a similar line at a later date, pro- 
vided the endeavor he then made was appreciated. 

The demand and the appreciation for the ^ 'blue ' ' 
book was greater than his anticipations, and the 
many letters asking to be remembered when an- 
other book was issued, have induced him to pro- 
duce a red book for the year 1899, and call it '^ An 
Outline of Ventilation and Warming. '^ 

The author has the honor to be the pioneer 
American writer of a book of reference on steam 
heating, etc. This book known as '^ Baldwin on 
Heating'' from the press of John Wiley & Sons, 
has now reached its 14th edition ; something tha^ 
no other engineering work ever printed in America 
has attained. 

(3) 



HEATING AND VENTILATION, 



Air Necessary for Ventilation of Habitations^ 
Schools^ and Ptiblic Buildings, 



THERE are at least two general classes of cir- 
cumstances that are the cause of vitiation to 
the air of habitations, and they may be divided 
into what can be called controllable and uncon- 
trollable causes. 

The controllable causes are those that can be 
removed by the occupants, or rather prevented by 
them, with proper attention to personal cleanli- 
ness, the cleanliness of the house and its appoint- 
ments and surroundings, and they consequently 
cannot come within the province of the archite6l 
or engineer (except in a very general way) when 
providing for the ordinary ventilation of buildings 
or habitations of any kind. 

The uncontrollable causes of the vitiation of the 
air of buildings or habitations are the natural re- 

(5) 



6 HEATING. 

suit of occupation, apart from what individual 
effort may do, and they should be the ones the 
architect or engineer is called upon to take 
into consideration when designing buildings 07 
other habitations. 

They are :— ■ 

ist. The exhalations from the lungs and trans- 
pirations from the skins of animals. 

2nd. The contamination due to the produ6ls of 
combustion from lamps, gas burners or other arti- 
ficial lights with combustion as a result : and 

3rd. The vitiation due to any special cause, such 
as cooking, manufacturing, the laboratory, the 
etherizing room, the hospital and the disinfecting 
room. 

The first, therefore, is an unavoidable and ever- 
present cause of vitiation from healthy as well as 
unhealthy persons, and it forms an ever-constant 
factor of vitiation per individual, calling for a cer- 
tain amount of fresh air per hour per person if 
some common standard of purity is to be main- 
tained, and it is this quantity, whatever it may 
prove to be, that should form the least quantity 



VENTILATION. 7 

that the architect and engineer should be called 
upon to provide for in ordinary buildings. 

In the estimates of fresh air per person by nearly 
all able writers on the subject, the amount re- 
quired for respiration and for skin transpirations 
is all that has been considered in their tables, 
though reference to the destruction of the air by 
lighting is not omitted in their writing. 

Ventilation, therefore, as spoken of below, will 
deal only with the amounts of air necessary for 
the removal of organic contamination due to man 
in a healthy state, and does not take into special 
consideration the sick room ; defective stoves or 
furnaces (that leak gases into the air of the house) ; 
defective plumbing fixtures or pipes, or impure 
cellar air that finds its way upward through the 
house, etc. , etc. , all of which when they exist re- 
quire a special or preventative treatment rather 
than a remedial one, and, therefore, all the tables 
or quantities of air mentioned hereafter are the 
minimum quantities necessary to keep the air of 
habitations purified to some ''''common standard of 
comparisons^ with the outer air, though in some 



b KEATI^XT. 

cases they may be the arbitrary estimates of persons 
who have been consiiered good authority on the 
snb;ect o: ventilation at the time they lived and 
wrote, bat may n:t n:w be considered ample. 

Doctor D. B. Reid. the gentleman who fol- 
lowed Sir Christ :r her Wreti, and the French sci- 
entist. Desag-aliers. in their eJorts to produce 
something like satisfactory- ventilation in the Brit- 
ish Honse c: Parliament, in the early part of the 
present century.', was the hrs: rerson in Great 
Britain :: advocate anything like the necessary- 
amount oz air per inai'.-iaual :::at later research 
and exrerience. ai:lei *:y :i:en:ical analysis, has 
since proved t: ':e necessary. 

He made the ar':i:rar}- estimate that ten cubic 
feet jZ fresh air per minute. :r i:: cubic feet per 
h:ur. f:r the respiratiin :f an adult person was, 
to use his cvm wcrfs, "' Certainly quite low enough 



Dr. xLlisha Karris Xevc York State Board of 
Health . while sreakin^ in the lig"ht of more re- 



LC_. r^. 



vleage :n this subject, said, when refer- 
in^ to Dr. Rerd's estimate fo: cubic feet', '' that 



VEXTILATIOX. 9 

with this allowance per capita the air of an apart- 
ment would become too vitiated for healthy res- 
piration at the end of an hour,'' and the question 
now is, ^' How very few of us have even this allow- 
ance of fresh air where we live and labor ? • ' and the 
second question then arises, ''If this is not ample, 
what is?" 

Able men have considered this subject, and after 
I have stated briefly their opinions as to the quan- 
tities of good fresh air required for different classes 
of habitations, I will proceed to illustrate the 
means ordinarily used by competent engineers to 
obtain ventilation in connection with heating ap- 
paratus, as in all cold countries, the two subjects 
must be considered together. 

Some writers always refer to the amount of fresh 
air required per minute per individual. It is bet- 
ter, however, for many reasons to familiarize our- 
selves with the amounts required per hour, and, 
therefore, all reference hereinafter made to quanti- 
ties of air, will mean the quantity required per 
hour, unless otherwise especially stated. 

General ]Morin, Director of the Conservatorv of 



lO BLEATING. 

the Arts and Trades, Paris, in his able work on 
warming and ventilating, says : ^'The amount of 
air to be changed every hour to preserve the 
healthful condition of rooms should be, for : Hos- 
pitals, 2,119 to 2,472 cubic feet, to be increased to 
3,700 during epidemics ; surgical wards and lying- 
in hospitals, 3,532 cubic feet ; prisons, 1,766 cubic 
feet ; work-shops, 2,119 cubic feet, to be increased 
in case of unhealthy trades to 3,532 cubic feet ; 
barracks and theatres (in the day-time,) 1,059 ^^" 
bic feet ; barracks (at night), 1,431 to 1,766 cubic 
feet ; assembly rooms for long sessions, 2, 200 cubic 
feet ; hall and lecture rooms, short sessions, 1,059 
cubic feet ; primary schools, 424 to 530 cubic feet ; 
adult schools, 883 to 1,059 cubic feet. 

Peclet, who wrote before Morin, allowed the 
same for hospitals, 2,120 cubic feet. In theatres, 
prisons and schools, however, he underestimated^ 
allowing only 300 cubic feet for living rooms and 
212 cubic feet for primary schools. 

Morin, speaking of his own estimates, remarks 
that they ' ^ are not at all excessive^ ' ' and this Pet- 
tenkofer has demonstrated scientifically since 



VENTILATION. II 

Morin wrote. I would not mention the names of 
Morin or Peclet at this time, were it not that they 
were capable and able men in their day, and that 
hence their estimates are still often looked on as 
ample by those who have not studied the subject 
in the light of later experience and experiments. 

The error many of the early investigators fell 
into was that they considered the admission of a 
measure of air equal to that vitiated as sufficient, 
or if not sufficient, that two or three times the 
amount would probably be so. 

Tredgold furnishes an illustration of this method 
of reasoning when he says : "' Taking the capacity 
of an ordinary pair of lungs at 40 cubic inches per 
respiration, and 20 respirations per minute, he had 
800 cubic inches per minute for respiration." 

For the transpiration from the skin he estimated 
that from 12 to 30 grains of moisture was given off 
in the same time, one minute, and that it would 
take three cubic feet of air per minute to absorb 
this moisture, estimating that the humidity or 
degree of saturation of the air would be sufficiently 
far from the dew point to allow the air to absorb 



12 HEATING. 

about ten grains of aqueous vapor per cubic foot. 
He further estimated that a candle would require 
about 300 cubic inches of air per hour for its sup- 
port, and sums up by saying that ^' four cubic feet 
per minute or 240 cubic feet per hour was the 
amount per person necessary for ventilation." In 
reality, it is not more than one-tenth enough for 
good ventilation. 

The fallacy of such a method of reasoning will 
be seen if we consider a vessel of clear water into 
which a small measure of coloring fluid has been 
discharged, say a bottle of ink into a tub of water. It 
is very evident that an equal amount of clear water 
thrown in will not restore the original clearness of 
the water in the tub, and, in fact, we are justified 
in saying that no amount — at least no practical 
amount — of water will entirely remove the traces 
of the ink. It may be diluted to a point of clear- 
ness sufficiently good for the purpose to which it is 
to be put, provided we run into it sufficient clear 
water, and it is the same with the air of our rooms. 
The individual turns 240 cubic feet of it as ^^ black 
as ink '' in every hour, and to make it sufficiently 



VKNTILATION. 13 

good for man to live in, we mnst add at least ten 
times as much pure air ; and then we will be tak- 
ing air into our lungs, air that contains one- 
tenth of the organic matter that the body gave ofif 
previously. 

The early investigators depended largely on the 
sense of smell as a guide to the vitiation of rooms. 
It is certainly of considerable help, though con- 
clusions drawn by such means must be as variable 
within certain limits as the persons who make them. 

Morinsays that in the Hospital Beaujon, with an 
admission of 530 cubic feet per bed per hour, there 
was a '' sensible odor.'' When the admission of 
air was increased to 880 cubic feet, the odor was 
' ' disappearing. ' ' His remark on the Military 
Hospital at Vincennes, with i,o6o cubic feet per 
bed per hour, was ' ' too little air. ' ' With 4, 240 
cubic feet in the same hospital he said there were 
^' draughts'' (because the air was improperly 
admitted,) and as a compromise between the 
** draught" and the *^ smell," he fixed the admis- 
sion at 2,120 cubic feet and pronounced it '^satis- 
factory. ' ' 



14 HEATING. 

I Will say here that had he admitted the air 
near the ceiling, he could have avoided the 
draughts, as the writer has done in the Sloane 
Maternity Hospital in New York, where over 
8,000 cubic feet per bed per hour is admitted in 
this manner unnoticed by the patients. 

With no better guide than the sense of smell, 
Peclet, in a report on the ventilation of the old 
Chamber of Deputies at Paris, pronounced 635 
cubic feet per head to be ^'satisfactory,'' supple- 
menting his remarks with ''no odor." The 
amount of organic matter, therefore, as detected 
by the nose is very uncertain, especially if one is 
in the room for any length of time, while on the 
other hand, the slightest trace of mustiness is de- 
tedled by a sensitive person on entering from the 
outer air ; and under these conditions Dr. de 
Chaumont, Assistant Professor of Hygiene, in the 
Army Medical School at Edinburgh, has shown 
by a large number of experiments — over 400 analy- 
ses—that the sense of smell, carefully employed, 
does give some idea of the amount of impurity in 
the air spaces of habitations. 



VENTII.ATION. 15 

During de Chaumont's experiments, the amount 
of carbonic acid (CO^) in the outer air was deter- 
mined, so that the respiratory impurities were ac- 
curately known. Dividing his observations into 
groups, he found that i^^^^ parts of carbonic acid 
(COg), due to respiratory impurities was ^^not no- 
ticeable '' in 10,000 parts of air; when it reached 
4.132 parts in 10,000 the organic matter was ^^ be- 
coming perceptible'' to the smell, and that at 6^ 
parts per 10,000, it was ^'disagreeable,'' while at 
9 parts (or nearly i in 1,000) it was ''offensive and 
oppressive;" "the limit of differentiation by the 
senses having been reached." 

It will thus be seen that when the carbonic acid, 
due to respiration, etc., has reached 2 parts in 10,- 
000, it is generally noticeable, and de Chaumont 
says, in Parks' Hygiene^ that "2 parts of coinci- 
dent * carbonic acid per 10,000 of fresh air should 
be the maximum amount of respiratory impurity 
admissible in properly ventilated rooms." 

Adopting this standard, Parks' Hygiene gives 
the following table of the quantities of pure air per 

* By coincident he means the amount caused by man in excess of the 
normal outside condition. 



lo HEATING. 

head that should pass through a room ou the basis 
of -y^ of a cubic foot of carbonic acid being exhaled 
by an average adult person in an hour. 

Tabi^k to show the degree of contamina- 
tion OF THE AIR (in terms OF CO^ ) BY RES- 
PIRATION, AND THE AMOUNT OF AIR NECES- 
SARY TO DII^UTE TO A GIVEN STANDARD OF . 2 
PER I, GOO VOI.UMES OF AIR, EXCLUSIVE OF THE 
AMOUNT ORIGINALLY PRESENT IN THE AIR. 



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2.00 


400 


1.50 


500 


1.20 


600 


1. 00 


700 


0.86 


800 


0-75 


900 


0.67 


1,000 


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3,000 


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2,200 


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VENTILATION. l^^ 

The -^-^ of a cubic foot of carbonic acid exhaled 
is from the experiments of Pettenkofer, who is 
considered the most trustworthy authority on this 
subjedl, and who found by the chemical analysis of 
the air in experiments on the body of a man 28 
years old, weighing 132 pounds, that ^^in repose '^ 
he gave out .00424 cubic feet of carbonic acid re- 
duced to the volume of 32 degrees Fahr. per pound 
weight of his body; while under ^^ gentle exer- 
tion'' it was found to be .00591 cubic feet ; and 
that it reached .01227 cubic feet for ^' hard work ;'' 
being nearly in the proportion of 2, 3 and 6 re- 
spectively. On the supposition, therefore, that the 
average weight of the human body is 142 pounds, 
we have from the above, 142 pounds x .00424 = 
.602 cubic feet of carbonic acid for a person '^in re- 
pose ;'' .9 cubic feetfor ^'gentle exercise," and 1.8 
cubic feet for '^ hard work.'' 

This, then, is the measure of ^^the vitiation" 
for healthy persons accepted by the prominent 
writers and thinkers of the day, and it is from this 
data that the table was compiled, as I believe, by 



l8 HEATING. 

de Chaumont. The temperature is taken as that of 
the freezing point of water. 

Analysis made in a room under the foregoing 
conditions (those shown in Table I), would there- 
fore, show 0.0002 of ^^ coincident " carbonic acid, 
and probably not less than 0.0004 additional car- 
bonic acid for the natural state of the outside at- 
mosphere, making in all about 0.0006 carbonic 
acid in the air of the room. 

It must be distinctly remembered the carbonic 
acid itself can scarcely be considered an impurity, 
and from the ventilating engineer's standpoint the 
excess (the coincident carbonic acid) found to exist 
within doors, over that existing outside, is only the 
measure of the organic impurities thrown off by 
the animal system, and that they exist in propor- 
tion to it. 

To prevent misconception, the carbonic acid al- 
ready in the atmosphere was disregarded in the 
table. 

De Chaumont' s formula on which it was calcu- 
lated is (Pi — P) ^ zzr: d, in which Pi = impurities, 



VENTILATION. 19 

or carbonic acid, per 1,000 volumes already in the 
air-space (c.) 

P = admissible limit of the respiratory impuri- 
ties — that is, 2 parts of coincident carbonic acid in 
10,000 of air ; c = air space in cubic feet ; d = 
amount of fresh air required per hour per indi- 
vidual. 

Park points out that for rooms occupied contin- 
uously, or for long sessions, that c in the above 
formula has an apparent importance it does not 
possess, and substitutes the following simple one, 
=5 =: d, in which e = the carbonic acid exhaled 
per person per hour ; P = the limit of admissible 
impurities from the lungs, etc. ; d = the required 
amount of fresh air in cubic feet per hour. 

If, then, e is taken at the general average of 0.6 
cubic feet (according to Pettenkofer), and the limit 
of coincident carbonic acid at .0002, we have 
7i."atW = 3,000 cubic feet per average person per 
hour, for persons in repose, which will become 
"V.¥w^=' 4^500 cubic feet for gentle exercise, and 
■^.*¥ot|- = 9,000 cubic feet for hard work. 

On this basis, therefore, of Pettenkofer' s .00424 



ZO HEATING. 

of carbonic acid per pound weight of individuals 
and the permissible maximum of ^'coincident'' 
carbonic acid placed at 0.0002, I have constructed 
the accompanying diagram which shows the whole 
subject almost at a glance, and enables the archi- 
te6l or engineer to pick out the quantity of air 
necessary for either children or adults, or for any 
person from 30 to 170 pounds in weight. The or- 
dinates of the line a-d indicate the quantity of air 
in cubic feet for persons in repose ; the line c-d for 
persons gently exercising, and presumably, persons 
writing or studying ; the line e-/' for persons 
doing hard work ; which line corresponds to the 
quantity of air ordinarily considered necessary for 
hospitals. 

There is no question in my mind but that children 
in schools studying, should be classed under the 
head of ' ' gentle exercise. ' ' Their minds are active, 
and their limbs are always in motion. I therfore 
consider the line c-d as indicating the quantities of 
air necessary for schools if the standard of purity 
is to be established or maintained on the addition 
of but two parts of carbonic acid to 10,000 of air. 



WEIGHT OF INDIVIDUALS IN POUNDS. 



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VENTILATION. 21 

The vertical line £''k shows the air required for 
schools under the Massachusetts law, and it has 
been added to the diagram for comparison. The line 
is vertical because weight of persons is not consider- 
ed. It is equivalent to maintaining a ^'standard of 
purity^' whose excess of carbonic acid would be 
about 4 parts in 10,000 of air, when the weight 
of the scholar is 130 lbs. 

All permanent reforms, however, have come 
slowly, and therefore if the persons in charge of 
our public schools will only adopt the lowest of the 
standards shown in this diagram, and advocated by 
Morin, Wyman, de Chaumont, Billings, Parks, 
Pettenkofer, and, in short, every man who has 
studied the question carefully, we will be making 
a great stride towards perfection, and a wonderful 
improvement over the present state of affairs in 
many countries. 

It will result in brighter and healthier children. 
They will learn faster and grow larger, and the 
teachers who have to live in the same atmosphere 
with them will be improved, physically and other- 
wise, as well as the children. Sore throats will 



22 HEATING. 

disappear, and sick headaches will be the excep- 
tion, not the rule. 

HEATING. 

B011.KR : In warming by steam or hot water, the 
boiler is generally the first consideration. 

Horse-power: What is known as the '^ boiler- 
maker's horse-power'' is usually taken at 15 square 
feet of surface, in fire-tube boilers, such as 'the 
horizontal multi-tubular boilers. 

The makers of large diameter (4 inch) water-tube 
boilers place a horse-power at between 11 and 12 
square feet of surface ; though recent practice is 
beginning to place it at 10 square feet. 

These, of course, are arbitrary ratings, and will 
vary with the conditions of draught, the proportion 
of grate to boiler, and surrounding conditions, but 
they are nearly correct for average conditions, and 
form good pradlice. 

Centennial horse-power : The centennial horse- 
power of a boiler is that quantity of surface that 
will evaporate 30 pounds of water from a tempera- 
ture of 100 degrees Fahrenheit, to steam at 70 



VKNTII.ATION. 23 

pounds pressure, regardless of the boiler surface 
that it requires to accomplish it. 

Mechanical Engineer's Horse-Power : The me- 
chanical engineer's horse power is the evaporation 
of 33 pounds of water from a temperature of 212 
degrees Fahrenheit to steam at 80 pounds pressure, 
which is nearly the same as the centennial horse- 
power. 

Evaporation in Boilers : The evaporation of 
water in boilers is ordinarily found to be between 2 
and 3 pounds of water per hour, per square foot of 
surface, under ordinary conditions of setting. A 
boiler can be forced to the evaporation of 4 or 5 
pounds of water per square foot of heating surface, 
but it is always attended with waste in fuel ; the 
greatest economy being obtained at between 2 and 3 
pounds of water per square foot of surface, per hour. 

Boiler Maker's Horse Power : When the boiler 
maker's horse-power is taken at 15 square feet of 
heating surface, it is only necessary that it shall 
evaporate 2 pounds of water per hour, per square 
foot, to make steam equal to the centennial horse- 
power. 



24 HEATING. 

Limit of Economy : When the boiler maker's 
horse power is taken at less than 15 square feet, the 
evaporation, of course, must be greater than 2 
pounds per square foot, and when the boiler 
maker's horse-power is placed as low as 10 square 
feet per horse-power, the evaporation to accomplish 
the centennial horse-power must be 3 pounds of 
water per square foot per hour ; when it has prob- 
ably reached the working limit of economy. 

Grate Surface to Boiler Surface : ] mi ^- c 

Boiler Surface to Grate Surface : t ^^^ ^^^'^ ^^ ^^^^^ 

surface to boiler surface varies between (i) of grate 

to fifty (50) of heating surface, to one (i) to thirty 

(30), for horizontal multi-tubiilar fire-tube boilers ; 

while for the ordinary 4 inch water-tube boiler, 

the ratio is about one (i) to thirty-five (35) ; 

the ratio for the well-known Babcock & Wilcox 

Water Tube Boiler being from i to 35, to i to 40. 

For the cast-iron heating boilers, it will vary 
between one (1) of grate to thirty (30) of heating 
surface, running down to less than one (i) to ten 
(10), in some types of cast iron boilers. 

As a general thing, the greater the proportion of 



VENTILATION. 25 

heating surface to grate, the greater the economy 
in the burning of fuel. 

Coal Burned per Square Foot of Grate : There is 
an idea that the most economical consumption of 
coal is obtained when it is burned on grates at the 
rate of between 8 and ten pounds per hour per 
square foot of grate. This, however, was obtained 
from a series of experiments, under boilers whose 
grate surface held about a constant relation to the 
heating surface, so that the economic relation be- 
tween coal and grate will vary with the relation 
between the area of the grate to the area of the 
heating surface of the boiler. 

In ordinary pradlice, however, it may be stated, 
that the economic limit in fadlory boilers, and 
where steam is made in large quantities for power, 
may be placed at 15 pounds of coal per square foot 
of grate per hour ; the range for power boilers be- 
ing from 10 to 15 pounds of coal per square foot of 
grate per hour. 

In the matter of heating boilers, the conditions 
are very different. In heating boilers, the ratio of 
grate to heating surface of boiler is larger than for 



26 HKATING. 

power boilers, while the ratio of consumption of 
coal per square foot of grate will drop down to as 
low as 2 and 3 pounds of coal per hour. The rea- 
son of this is that the furnaces are made larger so 
as to hold a large body of coal and maintain heat 
for long periods (8 to 12 hours) without attention, 
with scant draught and slow combustion. 

Relation of Chimney to Grate Surface: In power 
boiler practice, an arbitrary rule says that when a 
chimney is 100 feet high, it should be }4 of the 
grate area in its (the chimney's) smallest cross sec- 
tion. This seems to work fairly well for boilers 
down to about 50 horse-power, but with smaller 
boilers, the proportion of the chimney (under such 
an empirical rule) should have an excess of about 
50^, and it is good practice, never to provide a 
chimney of less than one square foot of cross sec- 
tion for boilers for heating apparatus. 

Draught in Chimney : The intensity of draught 
in a chimney varies directly as the square root of 
the height of the chimney (temperatures remaining 
constant,) so that corrections may be made accord- 
ing to this rule, for chimneys as they vary in 



VKNTILATION. 27 

height. In other words, when the height of the 
chimney is lOO feet, the intensity may be consid- 
ered as ID ; while at 150 feet, the intensity will be 
but 12^ ; while for 50 feet, it will be 7 ; so that 
the relation between chimney areas and grate areas 
will vary inversely as the square root of the height. 

Evaporation in Boilers per pound weight of 
Fuel : There is sufficient heat in a pound of good 
coal to evaporate 14 pounds of water, provided all 
the heat of the coal can be utilized. 

In pra6lice, however, there is only sufficient heat 
utilised to evaporate between 10 and 11 pounds of 
water to produce draught. In burning fuel, the 
heat that is carried off with the produ6ls of com- 
bustion and below the temperature of the steam is 
lost, except insofar as it makes draught, or is util- 
ized to warm the feed water. 

Proportioning Boilers : In proportioning boilers 
when the work to be done is known, first determine 
the rate of combustion per square foot of grate 
most desirable, say about 15 pounds per hour ; 
then determine the size of the entire grate on the 
assumption that you can evaporate 10 pounds of 



ZS HEATING. 

water per hour per pound of coal, which is the 
equivalent of 150 pounds of water per square foot 
of grate ; then, having the entire horse-power re- 
quired, say 100, at 30 pounds of water per horse- 
power, or a total of 3,000 pounds of water per hour, 
it will require just 20 square feet of grate for such 
a boiler. 

In determining the surfaces of boilers, it is better 
not to consider the question of ratio of heating sur- 
face to grate surface, but of heating surface to the 
water to be evaporated. 

Taking the water, therefore, at 3,000 pounds per 
hour, and 3 pounds of water per square foot of heat- 
ing surface as a maximum evaporation, the heating 
surface of the boiler would just equal 1,000 square 
feet, which should be increatsed to 1,500 square 
feet when the evaporation is to be only 2 pounds 
of water per square foot of surface per hour. 

The latter size boiler would probably have 30 
square feet of grate, and if it is only worked up to 
100 horse-power, would burn but 10 pounds of coal 
per square foot of grate per hour, while the ratio of 
the heating surface of the boiler to the area of the 



VENTILATION. 29 

grate still remains 50 to i, which in the judgment 
of the writer, is about the economical limit. 

Condensation in Radiators : It has been 
shown that the evaporation in boilers is between 2 
and 3 pounds of water per square foot of surface per 
hour. 

It is also well known by the experiments of com- 
petent engineers (see ^ ^Baldwin on Heating^ ' ' pag^ 
298) that the condensation in radiators varies from 
\ to -f-^ of a pound of steam (water) per hour, for 
low pressure steam (i to 5 pounds,) such as is used 
in heating, all of which established a fa6l that in 
determining the size of a boiler for a heating ap- 
paratus, it is well to provide boiler sufficient to 
evaporate one pound of water for every 3 to 4 
square feet of heating surface in the building. 

To have the boiler sufficiently large beyond 
question, so as to cover condensation in mains, etc., 
it is well to consider, therefore, one pound of water 
to every 3 square feet of heating surface, as the 
average condensation in the radiators and the evap- 
oration in the boiler. 

Therefore, by dividing the radiating surface 



30 HEATING. 

taken in square feet within the building by 3, we 
have the condensation in pounds of water per hour, 
and dividing the produ6l by 30, v/e have the capac- 
ity of the boiler in centennial horse-power. 

These conditions are for diredl radiation only. 

For indirect radiation, by natural draught, the 
condensation is about twice as great as for direct 
radiation, and with modern fan systems, the con- 
densation in the radiator is about four times as 
great ; while with hot blast high pressure work, 
the condensation may reach six times as much as 
for direct radiation. The latter, however, is not 
desirable, and is not good practice in warming 
buildings, though it may do for drying purposes. 

One pound of condensation per square foot of 
heating surface is a liberal allowance for fan or 
forced ventilation work, so that the relation be- 
tween surface of boiler and heating surface is in 
the proportion of from 2 of radiation (condensing 
surface) to i of boiler (heating surface), to 3 of radi- 
ation to I of boiler, according as the boiler is made 
to do more or less work. 

The foregoing on boilers, grates, chimneys. 



VKNTII.ATION. 3^ 

evaporation, condensation, etc., gives a general 
idea of what may be called the ^^ elastic limit '^ of 
the heating question, and to go much further 
would be to enter the domain of engineering, 
which is obviously not the intention of this work. 

Rules and methods, however, to provide ready 
and approximate data for the architecrt or designer 
who desires to find the first things necessary for the 
installation of a steam heating or ventilating ap- 
paratus, are within the scope of these articles, and 
I know no better way than to present some of the 
preliminary ones used in the drawing office of the 
writer. 

They are for heating and ventilating work for 
which pracftical and nearly accurate rules are re- 
quired. They are all based on stri6lly scientific 
and engineering data, but they are divested of all 
unnecessary refinement, which for ordinary pur- 
poses would only add complication to the task, 
without getting very much nearer the actual truth. 

To use these rules, the writer and the reader, 
should warm a building together. 

When a set of plans are placed on the drawing 



32 HEATING. 

boards, the first consideration is to determine the 
amount of condensation of steam that has to go on 
within a building, when that building is to be 
properly warmed by the particular method of heat- 
ing or of heating and ventilation that the owner or 
the architect may desire to adopt. 

It may be asked, ^^ Why is the question of con- 
densation the first consideration ? ' ' and in reply I 
will say, that it furnishes us with the first item of 
data on which to base all our other calculations. 
For instance, when we find the amount of cooling 
or condensation that is to take place within a 
building in the coldest weather, we can then 
readily find the amount of water that it will be 
necessary to evaporate to do this work. Having 
the amount of water that is to be evaporated, we 
can then obtain in any order we please, the size of 
the boiler necessary to evaporate the water ; the 
amount of coal or other fuel that will evaporate 
the same water ; the size of the grate on which to 
burn the coal ; the size and height of chimney 
necessary to supply air for combustion ; the size of 
the radiators necessary to condense the steam ; the 



VENTILATION. 33 

size of pipes necessary to convey steam or hot 
water to the radiators ; and all other attendant 
data which will develop as we proceed. 

Conditions for a School : Take, for in- 
stance, an ordinary primary school building of 
eight rooms, with say fifty children to a room, and 
our problem is to warm and ventilate this building 
so as to comply with what is known as the Massa- 
chusetts Law, which law provides that each occu- 
pant of the room has to receive a quota of thirty 
cubic feet of air per minute, which is equivalent 
to 1, 800 cubic feet of air per hour per child. This, 
therefore, on the basis of the minimum quantity of 
air allowed by law, making no allowance for the 
teacher, will call for the admission of 90,000 cubic 
feet of air per hour to the school room. Some 
allowance, however, should be made for the teacher, 
and also some for a factor of safety, so that it is 
both reasonable and safe for an architect or a 
designer to assume that he sould provide at least 
for the admission and the warming of 100,000 
cubic feet of fresh air each hour to each of the 
eight principal rooms of the school building. 






34 HEATING. 

Quantity of Air Required : This will call 
for 800,000 cubic feet of air per hour for the class 
rooms alone, and at least 200,000 cubic feet addi- 
tional should be provided for ventilation for the 
other parts of the building. Therefore, an eight 
room primary school will require about 1,000,000 
cubic feet of air per hour for its proper ventilation. 

Usually, enough warmth can be admitted with 
this quantity of air to keep the rooms properly 
and equitably warm, although it is customary to 
use additional direct radiation in the halls, etc., 
and in very cold climates, a little direct radiation 
in the form of long coils underneath the windows. 

Having now discovered the quantity of air neces- 
sary for the building, we have next to consider 
what its temperature should be as it passes through 
the registers. 

It is usual to maintain a temperature of 70 
degrees Fahr. within a room. It is a common 
thing to provide in specifications '' that the room 
shall be warmed to 70 degrees Fahr. when the 
thermometer outside is at zero.'' If the air passes 
the registers, however, at 70 degrees Fahr., it will 



VKNTII.ATION. 35 

not maintain the temperature of the room at 70 
degrees, as a certain amount of cooling goes on 
within the room, due to walls and windows. It is 
known, however, that should the air pass the 
registers at a temperature of 100 degrees, (giving 
the Massachusetts quantity of air) that it is some- 
what more than sufficient to maintain the tempera- 
ture of the room at 70 degrees, after the building 
is dry, even when the temperature outside is at 
zero. It is also known that air passing the 
registers at 80 to 85 degrees (giving the Massachu- 
setts quantity, say 100,000 cubic feet per hour for 
the room described) will not maintain the temper- 
ature of the room at 70 degrees, when the temper- 
ature outside drops much below 40 degrees. 

According to three (3) different theoretical rules 
(which it is not necessary to go into here) and 
assuming average conditions of w^alls and windows 
with light on two sides of such a room as we have 
selected, I have found that the air should enter the 
room at 27 degrees ; 16 degrees; and about 13^ 
degrees respectively above that at which the room 
is to be maintained ; but my experience has been 



36 HEATING. 

such that I place it at 30 degrees plus— that is^ 70 
degrees plus 30 degrees ; and therefore base all my 
calculations for school work on an increase of 100 
degrees above zero as the lowest safe temperature 
for which I provide means to warm the air. 

Air Units : Having therefore determined that 
the building requires 1^000,000 cubic feet of fresh 
air per hour warmed 100 degrees, we have as a 
result, 1,000,000 cubic feetx 100 degrees Fahr. = 
100,000,000, which of course is 100,000,000 cubic 
feet of air warmed i degree, and which we may 
call 100,000,000 '^ Air Units,'' the air unit being 
the equivalent of warming one cubic foot of air 
one degree Fahr. If now we divide these Air 
Units by 50, we have reduced the same to a value 
of 2,000,000 Heat Units ; the Heat Unit being the 
equivalent of warming one pound of water i degree. 

The Air Unit, however, above adopted, is an 
arbitrary unit, and to be correct should be based 
on warming a cubic measure of air at some constant 
temperature, say at 32 degrees or at zero, or the 
warming of some constant weight of air, irrespec- 
tive of its temperature or bulk. For our purpose 



VENTILATION. 37 

however, the divisor 50 is approximately correct, 
and is obtained thus :— 

One pound of air at 32 degrees Fahr. under a 
pressure of an atmosphere of 29.9 inches of mer- 
cury, will occupy a space of 12.38 cubic feet, and 
its specific heat is .2379 ; the specific heat of water 
being unity. In other words, a pound of water 
requires 4.2 times as much heat to increase its 
temperature one degree Fahr. as a pound of dry 
air does ; so that the warming of 4.2 pounds of air 
I degree is the equivalent of cooling one pound of 
water i degree. We have thus, one pound of air 
at 32 degrees Fahr., occupying a space of 12.38 
cubic feet x 4.2, which equals 52 cubic feet, or the 
bulk of air at a temperature of 32 degrees that can 
be warmed by i Heat Unit. This, as will be 
noted, is for air at 32 degrees. Now, if the air 
instead of being 32 degrees is zero, following the 
same method of reasoning as we have above, its 
bulk will be 48.6 cubic feet for each Heat Unit; 
and a temperature of 14 degrees above, its bulk is 
50 cubic feet ; while at 70 degrees Fahr. it will be 
56. 2 cubic feet. This therefore gives the range of 



38 HEATING. 

bulk for air between zero, the coldest outside tem- 
perature on which calculations are usually made, 
to 70 degrees, the temperature of the room, and 
shows why 50 can be taken as a proper divisor 
without appreciable error. 

British Heat Units : We have found above, 
therefore, that for every million cubic feet of air 
admitted to the building in an hour (or any time) 
and warmed 100 degrees, that we will have to fur- 
nish steam equal to 2,000,000 British Heat Units 
in the same time. To warm this quantity of air 
the equivalent of 2,000,000 Heat Units, we will 
have to cool a quantity of steam equal to 2,000,000 
Heat Units, and here again another average divisor 
of 1,000 may be used without appreciable error, by 
which we obtain the amount of steam necessary to 
be condensed (or water to be evaporated), and the 
answer will be in pounds weight of steam or water ; 
which, in the instance we have cited, is the equiv- 
alent of 2,000 pounds weight of steam condensed, 
or 2,000 pounds of water evaporated to steam in a 
boiler. 

Heat Units in One Pound of Steam : Let 



VENTILATION. 39 

US now see how this divisor of 1,000 is obtained. 
If we evaporate one pound of water from a temper- 
ature of 212 degrees (under our ordinary pressure 
of atmosphere) it requires 965 Heat Units to 
accomplish the evaporation, and to turn the water 
into steam at a pressure just above the atmosphere 
(according to Ragnault's tables) and if we look at 
any of the tables of the heat of steam, we will find 
that the latent heat of vaporization decreases with 
an increase of pressure, but that the sensible heat 
increases, and that the sum of the sensible and 
latent heat of steam above 2\2 degrees forms a 
nearly constant quantity, increasing slightly with 
the increase of pressure, so that at ten pounds 
pressure it is the equivalent of 974 Heat Units, and 
at forty pounds pressure it is the equivalent of 989 
Heat Units, while at one hundred pounds pressure 
it is the equivalent of 1,004 Heat Units, I follow 
this line of reasoning on the assumption that we 
always cool the water in the return pipes to 212 
degrees, or something below it. 

In low pressure apparatus it cools considerable 
below 212 degrees, so that it is only necessary to 



40 HKATING. 

cool it to 178 degrees to extract the whole 1,000 
Heat Units from it Therefore the divisor of 1,000 
(Heat Units) is obtained by cooling one pound 
weight of steam from say one pound pressure above 
atmosphere to water at a temperature of about 178 
degrees in the return pipes, and which would 
become but 1,004 heat units if we cool the steam 
from one hundred pounds pressure to a tempera- 
ture of 216 degrees in the return pipes. Therefore, 
the divisor of 1,000 is not empirical, but founded 
on correct science. 

If we therefore divide our 2,000,000 Heat Units 
by our constant of 1,000 (the Heat Units in a 
pound weight of steam) we find that we have to 
condense just 2,000 pounds weight of steam at any 
ordinary pressure, to supply our 2,000,000 Heat 
Units, necessary to warm the 1,000,000 cubic feet 
of air 100 degrees Fahr. 

HoRSE-PowKR : Having now discovered that 
we require to evaporate 2,000 pounds of water or 
condense 2,000 pounds of steam, we divide this 
2,000 by 30, and get the result in Centennial horse- 
power ; which is equivalent to 66.6 horse-power. 



VENTILATION. 41 

This, therefore, gives us the boiler capacity we 
have been looking for. 

CoAi. : After having found our boiler, it be- 
comes necessary to approximate the amount of 
coal that we may have to burn, so that we may be 
able to estimate our expense and also arrive at the 
size of our grate. Having the amount of water 
that it is necessary to exaporate, say 2,000 pounds, 
a simple method indeed is to divide the weight of 
water in pounds by another constant divisor of ten 
(10) and the result is the weight of good coal that 
will be burned to evaporate that quantity of water. 
This ten (10) is also a slightly variable quantity, 
and will vary from eight to eleveii with different 
types of boilers and kinds of coal. I use the ten 
for all ordinary calculations. Therefore, if we 
divide the 2,000 pounds of water by ten^ it shows 
that we have to burn about two hundred (200) 
pounds of coal per hour to warm 1,000,000 cubic 
feet of air 100 degrees in the same time. 

Grate : Having found the amount of coal to 
be burned, it then becomes necessary to establish 
the size grate necessary to burn this coal. It has 



42 HKATING. 

been said before that in burning coal under large 
boilers when a fireman is in attendance, that the 
greatest results in economy have been obtained 
when the coal has been burned at the rate of about 
nine pounds per hour per square foot of grate. For 
a low pressure apparatus in house work or school 
work in the care of janitors, and any apparatus 
that is made automatic and that will have to run 
for long periods without attention, four to five 
pounds of coal per hour per square foot of grate is 
ordinary practice ; hence the large proportion of 
grate in small boilers. Again, with high pressure 
power boilers, twelve to one, and even higher, is 
not considered bad practice. This question, there- 
fore, admits of great latitude, but for boilers for 
all ordinary large buildings (power boilers) ten to 
one and twelve to one, becomes a good rule. In 
other words, divide the amount of coal by ten or 
twelve, and you have the square feet of grate 
necessary and proper to burn it under average con- 
ditions of practice. 

The ten to one would give us twenty square 
feet of grate for a sixty -seven horse-power boiler. 



VENTILATION. 43 

which is rather a larger grate than a sixty-seven 
horse-power horizontal boiler would require, and 
where ten may be a good ordinary divisor, twelve 
will probably be nearer the ordinary and every-day 
practice, when circumscribed by local conditions. 

Chimney : The next question to consider is 
that of the chimney necessary to burn the amount 
of coal required. The chimney, when accurate 
data is required, should be calculated by the 
amount of coal to be burned and the height of the 
chimney, but this is a complex question in itself 
and we have no room for it just here. 

A common old rule for proportioning the size of 
the chimney for the grate, is to take one-eighth 
of the grate area, and call it ^^ chimney.^' Noth- 
ing was said about the height of the chimney, and 
at the best it is but a crude approximation, and 
often disappointing with short chimneys. It is 
one of the questions for an educated engineer when 
much is at stake. 

RECAPlTUIvATION. 

We may now review the whole of the foregoing 



44 HEATING. 

matter in the following simple manner by an 
arithmetical example, thus : 

(i) 1,000,000 cubic ft. air passing through 

building in an hour. 
X 100^ Fahr. air is warmed (o. to 

100 F.) 

50)100,000,000 Air Units. 



1000)2,000,000 Heat Units required in an hour. 



10)2,000 lbs. water to be evaporated in 
boiler or steam condensed in 

apparatus per hour. 

12)200 lbs. coal required per hour. 

8)16.6 sq. ft. of grate (minimum.) 



2.075 sq. ft., size of chimney 100 ft. 
high. 

The above speaks for itself. 

If now we desire to find only the Centennial 
horse-power of the boiler, we divide the number 
of pounds of water to be evaporated per hour by 
thirty^ thus : 
(2) 30)2,000 lbs. 

66. 6 horse-power. 



VENTILATION. 45 

B011.KR Surface : If again we desire to know 
the square feet of surface that such a boiler should 
have, to furnish 66.6 horse-power with ease, we 
may take ^^the boiler maker's rule'' of allowing 
fifteen square feet of surface per horse-power 
(which is the usual amount provided in horizontal 
multitublar boilers) and we have the following 
simple example : — 
(3) 66. 6 horse-power of boiler. * 

15 sq. ft. per horse-power. 



999 sq. ft. of surface in boiler, 
which is practically 1,000 square feet of surface for 
such a boiler. 

The foregoing simple data, therefore, establishes 
the amount of air necessary for the school ; the 
temperature at which provision should be made to 
warm it ; the total (British) units of heat necessary 
to warm the air ; the amount of water necessary to 
be made into steam (or steam to be condensed into 
water) ; the amount of coal required to be burned 
per hour ; the reasonable size of the grate on which 

*This boiler would be capable of being worked up to about 100 Cen. 
H. P. 



46 HEATING. 

to burn the coal ; the size of the chimney neces- 
sary for the same ; the power of the boiler in nom- 
inal horse-power, and the number of square feet of 
fire and flue surface in the boiler. 

The above is for indirect or fan work for school 
buildings, hospitals, etc. 

DATA FOR DIRECT RADIATION. 

The heating or direct radiating surfaces of a 
building should be proportioned to the cooling sur- 
faces, with of course an additional arbitrary allow- 
ance for air leakages or accidental ventilation and 
a fixed additional allowance sufficient to warm the 
air admitted or carried off when systematic venti- 
lation is provided. 

The cooling surfaces of a building are the out- 
side walls and windows and in cases of churches 
often the roofs. The judgment of the designer 
will suggest other cooling surfaces when they 
exist. The partition walls between warmed rooms 
of course should not be considered, and the cubic 
contents of a room play little or no part in the 
matter. 



VKNTII^ATION. 47 

It has been found that after the walls of a build- 
ing are dry, that a square yard of wall will cool 
about as much air as a square foot of glass. 

This, of course, is an approximation, differing 
with different construction, a furred wall passing 
less heat than one with the plaster on the hard 
wall. The ranges, however, are probably between 
5 square feet and 10 square feet to i ; that is, a 
wall may be so poor that 5 square feet of it will 
cool as much air as a square foot of glass, or it may 
be so good that it will require 10 square feet of it 
to cool as much as i square foot of glass. 

Now, it has also been found, that ^ square foot 
of average direct radiating surface, at low pressure 
steam (i or 2 pounds) will about offset the cooling 
of I square foot of glass in an ordinary window, 
in zero weather, without much wind when the 
radiators are properly disposed, so that with this 
data, we can approximate the direct heating sur- 
face for building, by allowing yi square foot of 
radiator for each square foot^ of the windows and 
for each 5, 7 or 10 square feet of wall, as in our 



48 HKATING. 

judgment we deem proper. To this^ however, 
must be added often as much as ^o% additional for 
accidental ventilation, through window and door 
leakages, for fireplace, and even for the movement 
of air through the walls of a building under wind 
pressure. Evaporation from walls of a new build- 
ing is an important factor of cooling, especially in 
the first winter. 

Having found or established the radiating sur- 
face, it is then necessary to know what the co;a- 
densation within a radiator amounts to. 

Horizontal coils of plain pipe, well distributed, 

have the highest efficiency as direct heaters. Then 
come the simple types of vertical radiators, when 
not of too great a height. The higher a radiator is, 
the lower its eificiency per square foot of surface, 
and thirty-six or thirty-eight inches has been 
established as a fair limit of height, so as to pre- 
vent an unnecessary waste of floor room, with 
reasonable economy in iron and in cost. 

Without going into the matter in detail, 
therefore, it is only necessary for me to say that 



VENTILATION. 49 

in horizontal one inch pipe in wall coils, the con- 
densation per square foot of surface is found to be 
about .3 of a pound of water per square foot per 
hour for low pressures (one or two pounds pressure 
of steam) and that it decreases to about. 25 of a 
pound of water per square foot per hour for the 
average types of radiators. 

Taking the value, therefore, of a pound of steam 
at 1,000 Heat Units, we have 300 Heat Units per 
square foot of surface for coils, which in some 
cases, run a little over this, and 250 Heat Units 
per square foot of surface for average radiators. 
The condensation, however will vary and increase 
with an increase of pressure of steam, and numer- 
ous experiments have demonstrated that the con- 
densation in different types of radiators and coils 
can be reduced to the equivalent of 1.66 Heat 
Units per degree difference, between the tempera- 
ture of the air of the room and the temperature of 
the steam, per square foot of heating surface, for 
the poorer types, to about 2.25 Heat Units for the 
more efficient direct radiators and coils. 



50 HEATING. 

Assuming, therefore, that we have a radiator of 
loo square feet in a room at 70 degrees, with a 
pressure of steam at one pound, or 215 degrees, we 
have a difference of temperature between the steam 
and the air of the room of 145 degrees, and should 
the type of radiators or coils be unknown to us, 
other than that the building is to be warmed by 
direct radiation, it is reasonable to assume that we 
may average the loss of heat per square foot of 
surface per degree difference of temperature at two 
Heat Units, which is my usual practice (unless I 
know exactly what type the radiators are to be) 
and which gives us a total loss of heat of .290 
Heat Units per square foot of surface, for a radia- 
tor of 100 square feet, therefore the loss of heat is 
equivalent to 29,000 Heat Units, or say the con- 
densation of twenty-nine pounds of steam, while 
for a building of 1,000 square feet of surface, it 
will amount to 290,000 Heat Units, and so on. 

For the sake of easy calculation, therefore, we 
will assume that we have a building with 10,000 
square feet of radiation, and desire to find the 
boiler, etc. we may proceed as follows : 



VENTILATION. 5I 

(4) 10,000 sq. ft. of radiation in building. 

290 Heat Units lost per sq. ft. per hour 

1,000)2,900,000 Total Heat Units. 

10)2,900 lbs„ Water to be evaporated or 
steam to be condensed per 

— hour. 

12)290 lbs. coal required per hour. 

8)24.16 sq. ft. of grate. 



3.2 Area of chimney in sq. ft. 100 
feet high. 

The horse-power of the boiler and the surface in 

square feet can be found as shown before in 

examples (2) and (3). 

APPROXIMATE RULES. 

Simple approximate rules based on the forgoing 

are : — 

HEAT UNITS. 

(i.) Having the cubic feet of air to pass through 
a building in an hour, and warmed 100 degrees 
Fahr., multiply it by two (2) and the answer is in 
Heat Units. 



52 HEATING. 

POUNDS WEIGHT OF STEAM. 
(2.) Having the cubic feet of air to pass through 
a building in an hour^ and warmed 100 degrees 
Fahr., desiring the weight of steam required to 
warm same, divide by 500, and the answer is in 
pounds weight of steam. 

COAIv REQUIRED. 
(3.) Having the cubic feet of air to pass through 
a building in an hour, and warmed 100 degrees 
Fahr., and requiring the amount of coal to be 
burned per hour, divide by 5,000, and the answer 
is in pounds weight of coaL 

SIZE OF GRATE. 
(4.) Having the cubic feet of air to pass through 
a building in an hour, and warmed 100 degrees 
Fahr., and requiring the grate area, divide by 
60,000, and the answer is in square feet of grate. 

SIZE OF CHIMNEY. 
(5. ) Having the cubic feet of air to pass through 
a building in an hour, and warmed 100 degrees 
Fahr., and requiring the chimney 100 feet high, 
divide by 500,000, and the answer is in square feet 
of cross sectional area of chimney. 



VKNMLATION. 53 

REQUIRED HORSE-POWER. 

(6.) Having the cubic feet of air to pass through 

a building in an hour, and warmed loo degrees 

Fahr., and requiring the horse-power of the boiler, 

divide by 15,000, and the answer is in horse-power, 

BOILER SURFACE. 
(7.) Having the cubic feet of air to pass through 
a building in an hour, and warmed 100 degrees 
Fahr., and requiring the number of square feet of 
heating surface in boiler, divide by 1,000, and the 
answer is in square feet, 

VENTIIvATlON THROUGH THE MEANS 
OF INDIRECT RADIATION. 

One cannot fully appreciate ventilation unless 
they have been entirely without it. 

In rudely built habitations, there is a larger de- 
gree of accidental ventilation than is ordinarily 
supposed. 

In well-built modern residences, the construction 
is often so good that it will hold water, hence the 
greater necessity for systematic ventilation. 

A case in point comes to the writer, in which a 



54 HEATING. 

grand New York residence was so air tight that the 
air to supply the grate fires had to come down the 
register flues, and when the fires were out, the air 
often came down some of the chimneys and passed 
to other chimneys or to the vent flues. In the 
kitchen of this house the air had to come down the 
ventilating flue of the hood of the range to supply 
the range fire until a window was opened. The 
kitchen floor was tiled and the walls and ceiling 
were marble. 

This building was warmed by diredl radiation 
with the exception of one indirect heater for main 
hall, which, of course, did not admit suflicient air 
to supply the fireplaces. 

In determining the quantity of air required for a 
private residence, it may be said that the engineer 
has no data to go by. The residence may be large, 
and the number of persons to occupy it may be 
small, and an average of two persons to a room 
would be too high for any kind of private resi- 
dences, excepting perhaps, the poorer apartment 
houses or tenements. 

There is probably therefore nothing left to the 



VKNTII.ATION. 55 

designer but to assume that two persons will occupy 
a bed-room, and that such bed-rooms will average 
some two to four thousand cubic feet of air in good 
residences. 

According to such a supposition therefore it 
would be only necessary to change the air in one 
of these rooms once or twice in the hour to give 
each person something like two thousand cubic feet 
of fresh air per hour, and if the whole house was 
treated in the same proportion, the change of air 
would be once in one-half hour to once in an hour, 
which when compared with school or hospital ven- 
tilation appears exceedingly small, though about 
the same per capita. 

My obje6l, therefore, in assuming conditions for 
a private house similar to those just given, is to 
show that it will not require such excessively large 
flues as some persons suppose, to secure very good 
ventilation in private houses. 

The general dedu6lion therefore to be drawn 
from the foregoing is, that when sufiicient warm 
air is entering or leaving a private residence to 
keep the house sufiiciently warm to be comfortable 



56 HEATING. 

in cold weather, that it is reasonable to assume 
that the house is receiving suf5Eicient fresh air to 
ventilate it to a reasonable standard of purity. 

The air entering the house is the vehicle of the 
heat. It is evident, of course, that the air is tak- 
ing sufficient heat from the indirect radiators or the 
furnace to keep the house warm, and this fa6l alone 
is presumptive evidence that sufficient air is com- 
ing in for ventilation. This diction has been 
questioned, still, I am forced in repeat it here, as I 
know it to be a fact, at least for private residences. 

This holds true for air entering the room at the 
registers up to a temperature of from 140 to 150 
degrees, and by finding the amount of heat that 
will be lost through the walls and windows of the 
building, one may estimate the amount of heat 
that is carried into the room or the building, by 
finding the number of cubic feet of air that it 
would be necessary to warm from the temperature 
the room is to be maintained at, to the tempera- 
ture at which the air passes the registers. There- 
fore, without the use of an anemometer, a close 
estimate of the quantity of air that enters a room 



VENTII.ATION. 57 

can be made, with no other data than the tem- 
perature of the room, the temperature at which the 
air passes the registers and the loss of heat through 
the walls and windows, the latter found in the 
usual way. 

This line of reasoning will also carry us consider- 
ably further, and it can be always used in approx- 
imating the amount of air passing into a school 
room without the use of an anemometer. For 
instance ; if the outside temperature happens to be 
zero, the temperature of the school room 70 degrees, 
and the temperature of the air passing the regis- 
ters 80 degrees, it is reasonable to assume that 
that room is receiving a quantity of air per child 
equal or exceeding the quantity required by the 
Massachusetts lyaw. 

It is also as reasonable to assume when it 
is found that the outside temperature is 30 or 40 
degrees (average conditions for winter weather in 
the neighborhood of New York) and that the air 
is found passing the registers considerably above 
100 degrees, (and that it is necessary to maintain 
a temperature so high to keep the room warm) 



58 HKATING. 

that it is not receiving sufficient air per capita to 
ventilate it to a standard of purity that is now 
considered sufficient by any reliable authority. 

Mixing Vai^vks : As indirect steam radiators 
or furnaces will warm the air that passes over their 
surfaces any place from 130 to 180 degrees it then 
becomes necessary, if ventilation is to be main- 
tained, that the air connot be admitted to the 
room at its initial temperature, and that some 
means must be provided for cooling it, (or chang- 
ing its temperature) to meet the requirements of 
the day or the hour, and called '^ mixing '' or tem- 
pering. 

Endeavors have been made to accomplish this 
in several ways, one of which was to use hot water, 
and try and regulate the temperature of the water 
to the conditions of the day. 

Another was to control the valves on the steam 
coils automatically, so that when the room passed 
the normal temperature, the coils were shut off 
and when it fell a few degrees, the valves were 
again opened. 

This applies to either steam or hot water. 



VENTILATION. 59 

though principally to the former, and gives fair 
results, the objection to it in the case of steam be- 
ing that it often results in cracking in the pipes at 
the times the valves are opened. 

x\ll things considered then, the mixing or switch 
valve which is nothing but a shunt in the air pipe, 
gives probably the best results. 

Figures No. i and No. 2 show two modifications 
of the switch valve in connection with a cold air 
inlet pipe, a radiator, a register and a school room, 
all of which can be operated by hand, '^/^" being 
the switch or shunt and ^"^ a^^ being the chain or 
pull ; which may be operated in various manners, 
the simplest of which is shown in the illustration. 
This requires the attention of the teacher. 

Figure No. 2 shows the method and valve used 
with automatic control, such as the '^Johnson 
Thermostatic Regulation.'' 

There are two ordinary butterfly dampers, {^' b^ 
^^^.'') so arranged that the cold air will pass 
through the under one and the warm air from the 
radiator through the upper one ; the thermostic 
contrivance (^^ 7"'') opening and closing the valves 



6o HEATING. 

and admitting alternately warm and cold air to the 
flue where it mixes and then escapes into the room. 
Of course, the prime object of a ''switch-valve'' 
is to be able to change the temperature of the air, 
while keeping the quantity of air admitted to the 
room constant. When a person closes the ordinary 
hot air register of an ordinary heating apparatus to 
modify the temperature of the room, he cuts off the 
air supply^ and this is the great defect in most 
indirect heating apparatus. 

Position of Hkat Registers : The question 
is often asked — ''Where should the warm air 
register be in a room ? ' ' and this may be answered 
broadly by saying, it matters little where it is, 
provided it will not cause inconvenience to the 
occupants. In private houses, it is generally 
placed near the floor, and of preference, it should 
be near the coldest side of the house. The floor 
system probably can only be tolerated where the 
air enters at a comparatively high temperature, 
and reduced quantity, and for this reason in the 
case of schools and hospitals, it is found that 
modern practice always places the register above 



MfimM^^mE^ 



St/MAI^/? VB/VT 






\ 







I I 







y/ /g <^/^/yJ < ^/^/^/^j;^^^ 



VENTILATION. 6l 

the head-line, as the quantity of air sufficient for 
school or hospital ventilation cannot, as a general 
thing, be admitted near the floor, on account of its 
low temperature^ without inconvenience to the 
occupants. Seven (7) to eight (8) feet, therefore, 
is considered the proper level for the lower edge of 
the heat register in schools and hospitals. 

When the register is above the head- line, it also 
permits of a smaller sized register than could be 
tolerated at the floor. It has been said that i^ 
feet per second is about the velocity at which air 
should enter a school or hospital without causing 
draught. 

This is not the case, however, when air is ad- 
mitted above the head-line, 1^2 to 2 times the area 
of the flue being good practice, with a velocity of 
4 to 6 feet per second through the register. 

School rooms are generally planned with win- 
dows on two sides, and many seem to think that 
the warm air register should be placed in one of 
the side walls as near a window front as possible. 
It is shown, however, with some degree of confi- 
dence, that this is not at all necessary. When the 



62, HEATING. 

warm air from a register enters a room at a high 
register, the air is projected some distance into the 
room. It then finds the ceiling, and begins to 
move across the ceiling in the direction of the 
windows and outer walls, down which it flows and 
returns across the floor, to concentrate again at the 
outlet or vent register. This produces a rolling 
motion or local circulation which tends to mix the 
air, and without making an assertion as to which 
is the best position, I will simply say, that when 
the air is delivered very close to the windows, it 
begins to fall and pass across the floor, and were it 
not that it does not immediately pass out, simply 
a proportion of it passing out and part of it diffus- 
ing and getting into the general circulation of the 
room, I would say that near the window was not 
the best place to admit it. When the warm air 
is admitted near the rear wall or through the rear 
wall, it finds the ceiling, passes to the windows, 
passes down, passes across the floor and apparently 
does more to produce mixing and diffusion than if 
admitted at the front. The register in either posi- 
ion, however, being 4 or 5 feet from the ceiling. 



VENTII^ATION. 63 

generally discharges air sufficiently low and with 
sufficient velocity to disturb the entire amount of 
air just above the head-line. It is then taken into 
the circulation before explained and carried to the 
floor-line, each person thereafter being a means of 
mingling the floor air with the ceiling current 
again ; the body supplying the heat to produce the 
upward current. This motion is shown by the 
diagram. 

Position of Ventilating Registers : Where 
should the ventilating registers be in a room ? 
The opinion prevails among the best informed, 
that if we are confined to one vent register, it is 
best to withdraw the air from a room close to the 
floor and almost below where the air is admitted ; 
certainly in the same wall. This seems to favor 
school construction in a general way. 

A floor register should be at the floor ; not in the 
floor, but in the side wall at the floor ; and to 
obtain the best results, should cut down through 
the baseboard with its lower edge level with the 
floor. An endeavor should also be made to have 
the floor ventilating register as wide and as low as 



64 HEATING. 

possible. When flues are large, they require large 
registers, which means with the ordinary form of 
register, that the air is passing out under the upper 
edge of the register at between i8 and 30 inches 
from the floor, often leaving a cold stratum of air 
at the floor, causing cold feet to children. When 
the construction will permit, the register should 
never be more than 16 inches in height, with the 
longest diameter across the flue. This, however, 
is rarely permissible in ordinary wall construction, 
so that it is sometimes necessary to leave out the 
fret-work entirely, using nothing but a frame, and 
finish into the air flue with plaster or iron in the 
case of schools. 

Is it necessary to have a ventilating register near 
the ceiling in schools? Some authorities think it 
is not, though very few designers dare to leave it 
out altogether, and for this reason there is gener- 
ally a compromise, by putting a somewhat smaller 
register than the one used at the floor in the vent 
flue near the ceiling, with chains and valves so 
that it may be closed. Of course, in winter time, 
this register should not be left entirely open. If 



vp:ntilation. 65 

it does, it results in robbing the room of both heat 
and fresh air. It is therefore provided with means 
of closing it, and the responsibility of closing it 
remains with the teacher. In summer time, of 
course, it may be opened with advantage. 

Hospitals should be provided with registers near 
the ceiling as well as at the floor, so that ''flush- 
ing'' could be resorted to at times, even if the 
ceiling registers were not kept constantly open. 

To prevent too great a loss of heat at the ceiling, 
however, the designer should use some discretion 
in proportioning the ceiling registers, so that too 
much of the heat and fresh air would not escape 
that way ; if the registers are neglected. 

Doctor Dalton, Dean of the College of Physi- 
cians & Surgeons, at the time the first Sloane 
Maternity Hospital was built, when working on 
the matter with the writer, came to the conclusion 
that the ceiling registers should all be omitted. 

It was found, however, in certain small confine- 
ment rooms, that when chloroform was used, par- 
ticularly at a time when the gas was burning, that 
ceiling registers were an absolute necessity, the 



66 IIKATING. 

formation of clorine gas being a result of the com- 
bination of chloroform with the products of com- 
bustion ; the excess of which gas had to be drawn 
away at the ceiling to make the rooms useful. 
This, at least, is a case where ceiling ventilation 
was an absolute necessity, so that when the second 
part of the building was constructed, ceiling ven- 
tilation was provided in all the rooms and wards, 
their use being left to the judgment of the doctors. 

In auditoriums where fresh air is admitted in 
large quantities, through many small places under- 
neath the seats we find another condition which 
always requires ceiling ventilation. 

Forced Ventilation (Fans) : The term 
'^ forced ventilation '' signifies that the air is forced 
into a building with a fan or blower. 

The disc fan, which is nothing but a screw pro- 
pellor, will move large quantities of air under very 
slight resistance — a pressure equal to a ^ of an 
inch of water being about the maximum. It can- 
not be used to advantage when forcing air through 
a system of sheet iron flues that have any consider- 
able length. 



VENTILATION. 67 

The centrifugal fan, which is a paddle-wheel, 
and which sends the air off the edge of the blade 
by centrifugal force, is used as an intermediate 
pressure fan, controlling air pressures between yl 
inch of water pressure and 2 inches of water press- 
ure ; the inch of water pressure being, of course, a 
wind pressure capable of sustaining a column of 
water one inch in height. 

This class of fans can be run at a speed capable 
of sustaining these pressures without undue noise. 
The same type of fan housed, and run at very 
high speeds are called pressure blowers, and for air 
pressures other than ventilation can be used suc- 
cessfully up to about 4 ounces. The objedlion, how- 
ever, to using any type of centrifugal fan for high 
pressures is the enormous expense for maintenance 
when the volocities are high, the power required 
increasing in a ratio between the square and the 
cube of the velocities. The economical limit for 
centrifugal fans therefore, can be placed at about 
one inch of water pressure, and no ducts for carry- 
ing air through buildings should be designed that 
would require a greater pressure to move the air 



68 HEATING. 

successfully through them ; ^ inch of air pressure 
forming probably the best reasonable practice. 

The housed centrifugal fan or blower when 
throwing air from the tip of the blade, sends it 
against the case, where it rebounds and has to be 
carried around by the paddle wheel to the delivery 
port ; which results in a great waste of power. 
For this reason, duplex cone fans of the centrifugal 
type, which discharge the air in a forward direc- 
tion, being a compromise between the centrifugal 
fan and the propeller fan, will move more air at 
less cost than any other type of centrifugal fan. 
They have the advantage of delivering large quan- 
tities of air with comparatively slow velocities, thus 
doing away with annoying air vibrations which are 
carried through the air passages. They are capable, 
when run at the same speed as the housed blower, 
of delivering air at as high pressures, and when 
it is desirable to run them at slow speeds, by 
simply widening the blades, they secure increased 
quantities of air at very much less cost of power ex- 
pended than housed fans. They are now fast com- 
ing into use, their value being fully recognized. 



VENTILATION. 69 

PIvENUM VENTILATION. 
When the air is forced into the building, it is 
generally known as "- plenum '' ventilation, for the 
reason that the pressures are slightly above the at- 
mosphere, causing the air to escape, not only by the 
systematic vent flues, but often by any accidental 
opening. By this method, the engineer is able to 
se/e^ the place from which he takes his air supply. 

EXHAUST VENTILATION. 

Exhaust ventilation is that in which fans are 
placed at the top of the house, or in the ventilating 
flues, lessening the pressure within the building, 
producing a slight vacuum. It is sometimes nec- 
essary to exhaust buildings in this way, but ex- 
haust ventilation should never be used entirely to 
the exclusion of plenum ventilation, for the reason 
that if one produces a slight vacuum in the build- 
ing, air will enter through all openings, thus pre- 
venting the engineer from selecting or controlling 
the air supply ; and the writer has known cases 
in his own practice, where exhaust ventilation was 
capable of drawing the air from the soil pipes 



70 HEATING. 

through the trap in the water-closet fixtures. In 
like manner, if there are accidental leaks in the 
sewerage or soil pipes of the building, contamina- 
tions are sure to enter. The same applies to cess- 
pools and drains or neighboring contaminations of 
any kind ; while with plenum ventilation, the air 
of the building is made to enter the accidental 
breaks in the sewer pipes and pass out of the build- 
ing through the accidental openings. 

When the two systems have to be used in com- 
bination, the plenum system should have such a 
preponderance, that there would be no chance of the 
vacuum system drawing foul air into the building. 

There should probably be an exception to this 
rule in the case of dissecting rooms, laboratories, 
or other exceedingly foul sections of a building. 
It sometimes becomes necessary to exhaust these 
parts of the building, or at least to have less press- 
ure in them than in the other rooms, so that the 
foul air or smells will not pass from the dissecting 
rooms to the remainder of the building, but rather 
press into the dissecting rooms or laboratories. 

Wm. J. Bai^dwin. 



Card BY thb Author. 

THE author offers his services as an Expert and Designer 
of heating, cooling and ventilating plants and general 
engineering. 

He has had thirty years experience, both pradical and the- 
oretical, with a thorough knowledge of all the minutia of detail 
of constru(5lion. His experience enables him to assure econ- 
omy, both in design and maintenance. 

Below are a few of the buildings for which he has furnished 
plans, specifications, etc 

Vanderbilt Memorial Hall (Yale College,) New Haven, Conn. 

The (new) College of Physicians and Surgeons of the City of New York. 

The Vanderbilt Clinic, New York. 

The Sloane Maternity Hospital, (old and new,) New York. 

The W. & J. Sloane Carpet Store, New York. 

Lawyers' Title Insurance Co.'s Ofiice Building, New York. 

Hanover Fire Insurance Co.'s Office Building, New York. 

The Metropolitan Telephone and Telegraph Co.'s Office Building. 

Mechanics Bank Office Building, Brooklyn. 

Exchange Office Building, New Haven, Conn. 

New Laboratory, College Physicians and Surgeons, N. Y. 

Wm. J. Syms Operating Theatre, (Roosevelt Hospital,) N. Y. 

Columbia College Medical Department (easterly and westerly extensions). 

American Theatre, New York. 

Manhattan Co.'s and Merchants' Bank Office Building. 

The Importers' & Traders' Bank. 

U. S. Army Barracks and U. S. Army Mess Hall, David's Island, New York 

Harbor. 
George Street Public School, New Haven, Conn. 
Norton Street Public School, New Haven, Conn. 
Public School, No. 3, Paterson, N. J. 
Lemair Schwartz, Factory Building, N. Y. 
Messrs. Abraham & Straus, Great Department Store, Brooklyn. 
Leggett Office Building, Brooklyn. 
Ellis Island U. S. Emigrant Station, N. Y. Harbor. 
Madam De Hirsch Home for Working Girls, New York. 
' ' No. 7 Wall Street, ' ' Building of W. Wheeler Smith, Architect. 
Robert Hoe Building, New York. 
Hundreds of other large buildings and residences throughout the United 

States. 
Consulting Mechanical Engineer Electric Subway Companies, N. Y. 

m^-TEBMS FURNISHED ON APPLICATION. 



